Sometimes the story behind a movie is more interesting than the movie itself.

So it is with “The Promise,” a pet project of the late Kirk Kerkorian (one one of the architects of modern Las Vegas and past owner of the M-G-M Studio), who devoted years and a chunk of his fortune to create a film about the Armenian genocide of 1915-’20.

Never heard of the Armenian genocide? Join the club. Giving ill-educated audiences a glimpse of this swept-under-the-rug apocalypse is “The Promise’s” very reason for being. (Kerkorian was the son of Armenian emigres to the U.S.)

Historians estimate that 1.5 million Armenians — members of a Christian minority within the Ottoman Empire — were systematically murdered during World War I.

To this day the Turkish government refuses to acknowledge that the slaughter — many see it as a sort of dry run for Hitler’s “final solution” — even took place.

In fact, a well-financed disinformation campaign currently is underway to dismiss the history presented in “The Promise.” After several preview screenings earlier this year, the film’s IMDb page was flooded with more than 86,000 user reviews, with nearly two thirds of them negative. Apparently 86,000 persons showed up for a handful of preview screenings…not!

Clearly, “The Promise” is punching buttons. But how is it as a movie?

Just O.K. This David Lean-ish effort (penned by Robin Swicord, an Oscar nominee for “The Curious Case of Benjamin Button”) offers a three-way romance set against the sweep of churning world events (see “Dr. Zhivago”). It’s been directed by Terry George, who a few years back gave us the equally earnest “Hotel Rwanda” about tribal genocide in Africa. Production values are generally good, and in some instances outstanding.